If you've ever had the airlines lose your luggage, and it's only a matter of time until they do if you've been lucky so far, then you know that when you file a claim you're asked to describe your bag. "Umm, it's black and about this big," you say, making a box-like shape with your hands.
It turns out that there are standard ways of describing luggage, but that's arcane knowledge that you and I aren't hip to. Instead of memorizing if you have a Pullman or a trolley, just take out your iPhone and show the person behind the counter a photo of your bag. Then ask them how they'd describe it. They're professionals and spend their entire day figuring out how to distinguish between hundreds of look-alike bags, so what they say is what you want to write on your form.
Taking a photograph of your bag is best, because it will also show the bright pink ribbon you tied on the handle, but you can also use a photo from the manufacturer's website, as I've done for my beloved Filson bag, shown here.